1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a method for fabricating a touch panel integrated liquid crystal display device. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for improving misalignment between a polarizer and a touch panel.
2. Discussion of the Related Art
In order to make an efficient use of various electronic devices, touch panels for inputting signals on a display screen of a display device without any separate inputting device, such as a remote controller, has been widely used. More specifically, a device having a display screen is formed on flat display devices, such as liquid crystal display devices (LCD's), plasma display panels (PDP's), and electro luminescence (EL) displays, and conventional display devices such as cathode ray tubes (CRT's), namely a touch panel, thereby allowing a user to select desired information while viewing a picture.
Particularly, touch panels that are integrated with or added to computers, portable transmission devices, spherical and non-spherical display devices and other personal digital assistants (PDA's) are described as an input device. Unlike other input devices, such as a mouse or a keyboard, the inputting process of the touch panels is simple, misoperations are much less, and characters can be manually input.
The recently developed touch panels provide high reliability, new functions, durability, and precise technologies, such as technologies related to fabrication processes including handling materials and substances, and designing and processing techniques, rather than other typical functions of a touch panel.
The above-described touch panels can be categorized as an analog resistive type, a digital resistive type, a capacitive type, a supersonic type, an infrared sensor type, and an electromagnetic induction type, depending on the method of detecting a touch on the touch panel.
The parent structure of the touch panel includes an upper transparent substrate having an upper electrode, and a lower transparent substrate having a lower electrode. The upper transparent substrate is mounted on the lower transparent substrate so as to provide a space therebetween. Therefore, when an inputting means, such as a finger or a pen, touches a specific point on the upper substrate, the upper electrode of the upper transparent substrate and the lower electrode of the lower transparent substrate are electrically connected to each other. Subsequently, a controlling device reads a voltage changed by either a resistance or a capacitor at the touching point. Thereafter, a position coordinate is located based on the change in the potential difference.
The related art analog resistive layer type touch panel will be described with reference to the accompanying drawings.
FIG. 1 illustrates a plane view of a touch panel of the related art, and FIG. 2 illustrates a cross-sectional view taken along line I-I of FIG. 1, showing a resistive layer type touch panel 100 formed at a display surface of a liquid crystal display device to be used as a signal inputting means.
As shown in FIGS. 1 and 2, the touch panel includes a viewing area VA corresponding to the display surface of the liquid crystal display device, and a dead space DS surrounding the edge surface of the viewing space VA. In the dead space DS, the upper and lower substrates 110 and 120, each formed of a poly-ethelene-terephtalate (PET) layer, are spaced apart and bonded to each other by an insulating sealant 130. An upper transparent electrode 111 and a lower transparent electrode 121 are formed on the inner surfaces of upper and lower substrates 110 and 120, respectively, thereby having a rectangular shape corresponding to the viewing area VA. In addition, a signal line 140 applying a voltage to the upper and lower transparent electrodes 111 and 121 and reading a voltage change based on a randomly touched position, is connected to one of the upper transparent electrode 111 and the lower transparent electrode 121 in the dead space DS and extended to the outside. A plurality of dot spacers 150 formed of an insulating synthetic resin, such as epoxy resin, acrylic resin, and the like, is formed to be spaced apart from one another so that the upper and lower transparent electrodes 111 and 121 are not touched to each other with an unintended slight pressure.
Therefore, when a pressure is applied to a specific point on the upper substrate 110 by a pen or a finger, the upper and lower transparent electrodes 111 and 121 touch each other at the specific touched point. Subsequently, a voltage changed by the resistance value at the touched point is output through the signal line 140. In addition, when the user's hand or finger unintentionally touches the operating surface, the dot spacers 150 prevent the unintentionally touched point from being detected as a touched point.
FIG. 3 illustrates a cross-sectional view of the related art touch panel integrated liquid crystal display device. The touch panel integrated liquid crystal display device includes a lower polarizer 310, a liquid crystal panel 320 having a lower substrate 321 formed on the lower polarizer 310 and an upper substrate 322 formed on the lower substrate 321, an upper polarizer 330 formed on the upper substrate 322, and a touch panel 100 having a lower substrate 120 formed on the upper polarizer 330 and an upper substrate 110 formed on the lower substrate 120. Additionally, a case top 340 is formed on each side surface of the entire structure and edge portions of the touch panel 100.
The upper substrate 322 and the substrate 321 of the liquid crystal panel 320 each includes a color filter array (not shown) and a thin film transistor array (not shown). A liquid crystal layer (not shown) is filled between the upper and lower substrates 322 and 321.
Additionally, as shown in FIG. 2, upper and lower transparent electrodes 111 and 112, a plurality of dot spacers 150, and an insulating sealant 130 are formed between the upper and lower substrates 110 and 120 of the touch panel 100.
A method for fabricating the touch panel integrated liquid crystal display device shown in FIG. 3 will now be described in detail.
FIG. 4 is a plane view illustrating the laminating process of a touch panel and a polarizer in fabricating the related art touch panel integrated liquid crystal display device.
As shown in FIG. 4, a film type polarizer integrated touch panel 100+330 is formed by laminating the completed touch panel 100 to the upper polarizer, which is cut to fit the size of the touch panel, using a laminator. Subsequently, the polarizer integrated touch panel 100+330 is attached to the upper surface of the liquid crystal panel 320 having the upper and lower substrates 321 and 322 bonded to each other, and the lower polarizer 310 attached to the lower surface of the lower substrate 322.
Alternatively, the upper polarizer 330 is first attached to the upper surface of the liquid crystal panel 320, and the completed touch panel 100 is then laminated to the upper surface of the upper polarizer 330.
The method for forming the polarizer integrated touch panel 100+330 will now be described in detail.
As shown in FIG. 4, the touch panel 100 completed as a single body and the upper polarizer 330, which is cut to fit the size of the touch panel 100, are prepared.
The touch panel 100 is formed of a parent touch panel having a plurality of unit touch panels. The upper polarizer 330 is formed of a polyvinyl alcohol (PVA) layer having a two-tone coating material, such as iodine or a two-tone colorant, adsorbed and aligned thereon, and a triacetyl acetate (TAC) layer acting as a passivation layer disposed on the upper and lower surfaces of the PVA layer to be attached and bonded thereto.
As described above, the parent touch panel and the upper polarizer are cut into a plurality of units prior to the laminating process.
Subsequently, the touch panel 100 each cut and completely formed into a single unit size, and the upper polarizer 330 cut to align with the size of the touch panel 100 are attached to one another other by using the laminator. When the laminating process is carried out during the fabrication process, the touch panel 100 and the upper polarizer 330 can be attached to form different structures, as shown in FIGS. 5A to 5C.
FIG. 5A illustrates a precise alignment of the touch panel 100 and the upper polarizer 330. However, when laminating the touch panel 100 and the upper polarizer 330 each formed separately, the touch panel 100 and the upper polarizer 330 tend to be misaligned, as shown in FIG. 5B. Occasionally, as shown in FIG. 5C, the upper polarizer 330 may also be formed to have a size that does not correctly aligned with the touch panel.
Therefore, the above-described related art touch panel integrated liquid crystal display device having a polarizer is disadvantageous in that when laminating the touch panel and the upper polarizer, each being formed separately, the problem of misalignment and/or difference in size may occur.